1. Field of the Invention
The present invention relates to a static-image signal generation apparatus for obtaining static images having a small amount of image blur by using fuzzy theory.
2. Description of the Related Art
There has previously been known an apparatus that allows image signals to be recorded on a magnetic tape or magnetic disk or to be stored in CCD memory, MOS memory, magnetic bubble memory, or storage devices such as IC memory, and allows the image to be displayed. As an apparatus for specifically obtaining static images, examples of the prior art which are disclosed in Japanese Patent Laid-Open Nos. 49-52912 and 54-910510 have been known. In addition, an electrophotographic camera of the same type as above which is capable of regeneration immediately after photo-taking and capable of taking a photography again, is disclosed in Japanese Patent Laid-Open No. 57-44374.
However, in these apparatus, no small number of cases where the movement of an object is fast in comparison with the shutter speed since recording or storage is performed by pressing the release button, or where image blur occurs in photo-taken static images owing to the fact that an image pickup device moves after shutter operation, so-called camera-shake, and the image must be photographed again. For example, when a fast-moving object is photographed by using a device of an interlaced scanning type as an image pickup device, a drawback arises in that flickering occurs since different images are recorded from field to field, and thus an image which is extremely difficult to see is obtained.
In relation to this drawback, an apparatus is disclosed in U.S. Pat. No. 4,272,787 which is arranged to detect the movement of an object and perform frame freeze when the object is not moving and perform field freeze when the object is moving in order to prevent the inter-field flickering at static image storage time. However, since this apparatus field-freezes automatically when the photographed object is moving, this apparatus has a problem in that its resolution in the perpendicular direction deteriorates as regards a moving object.
In recent years, with the advancement of solid-state image pickup technology, pixels have been formed having a high density and chips have been miniaturized, with the result that an endoscope has been developed in which a solid-state image pickup device is mounted at the front end, i.e., an electronic endoscope. This device is inserted into a body cavity and used to observe places to be examined. It has the function of recording the observation image of such place. Not only the observation function, but the quality of the image is very important and exerts a major influence on the diagnosis of the place to be examined. Accordingly, in recording, an operator of the endoscope freezes the image of the place to be examined several times while a patient is made still, selects a most appropriate image as a record image, and records static images in a photo-taking apparatus and a video printer for a monitor image, a still video floppy device, and so on. However, even if a patient is made still, a place to be examined may move in no small amount as long as it is a living body being observed. In order to eliminate an image blur caused by this movement, a problem in that freezing must be performed many times arises.
The deterioration of a record image due to the movement of an object occurs differently depending upon the type of image pickup device and the image pickup method. For example, if a frame transfer type CCD (hereinafter referred to as an FT type CCD) is used as an image pickup device, the movement of an object in an exposure period causes an image blur. If interlaced scanning is performed by using an interline type CCD (hereinafter referred to as an IT type CCD), flickering resulting from the difference in inter-field images occurs in addition to the image blur caused by the movement of an object during the exposure period. In a so-called color frame sequence method in which a monochrome CCD is mounted in the front end of it and illumination light is made into, for example, RGB sequential light, in order to make the size of an endoscope smaller, since images of each of the primary color of RGB, which are photographed chronologically in sequence, are simultaneously displayed, a problem arises, namely, the movement of an object causes a deviation in color when an object is displayed--a so-called color deviation.
To solve the above-described problem, an apparatus has been proposed, by means of which image blur (color deviation) with respect to image signals input within a certain specific period is detected, and an image signal possessing the smallest amount of image blur is displayed on a monitor, etc. as a static image, rather than a static image being displayed on a monitor, etc. at the same time the freezing function works.
However, when a body cavity is observed by means of an endoscope device and the static images of the observed images are recorded by the device, an observation image of a large intestine moves scarcely, an observation image of bronchus moves slowly back and forth at each breathing (when observed by a directly observing type endoscope), and an observation image of a stomach moves peristaltically, and an observation image of an esophagus moves fast because of the respiration of esophagus and pulsation. The amount of movement differs depending upon the difference in the angle of view of each endoscope even at the same observation place. Therefore, the following problems exist. If the detection time for a minimum value is fixed to be constant, the detection time becomes insufficient for a fast-moving image. The detection time is left over for a scarcely moving image, and the next action cannot be performed until the set time is finished.
For this reason, this assignee has proposed an apparatus in Japanese Patent Laid-Open No. 63-286322, in which a minimum value detection means that detects a minimum value of the amount of movement from a movement detection means and a detection time setting means that sets the operating time of this minimum value detection means are disposed so that an image having a smallest amount of movement in a detection time which can be set to any can be stored or recorded.
According to this example of the prior art, an image having a smallest amount of movement is least in a set detection time can be stored or recorded. However, if the detection time for a minimum value is fixed to be constant, the detection time becomes insufficient for a fast-moving image. Conversely, the detection time is left over for a scarcely moving image, and a problem arises in that the next action cannot be performed until the set time is finished.
In addition, even if a detection time is changed for the movement of individual observation places, when movement characteristics vary, for example, the movements are greater or smaller than was expected, a problem occurs in that the detection time is not an appropriate time.